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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

On point-weighted designs

Horne, Richard Brian Denison January 1995 (has links)
A point-weighted structure is an incidence structure with each point assigned an element of some set W C Z+ as a 'weight'. A point-weighted structure with no repeated blocks and the property that the sum of the weights of the points incident with anyone block is a constant k is called a point-weighted design. A t - (v, k, Aj W) point-weighted design is such a structure with the sum of the weights of all the points equal to v and the property that every set of t distinct points is incident with exactly A blocks. This thesis introduces and examines this generalisation of block designs. The first chapter introduces incidence structures and designs. Chapter 2 introduces and defines point-weighted designs. Three constructions of families of t - (v, k, Aj W) point-weighted designs are given. Associated with any point-weighted design is the incidence structure on which it is based - the 'underlying' incidence structure (u.i.s.). It is shown in Chapter 3 that any automorphism of the u.i.s. of a t - (v, k, Aj W) point-weighted design with more than one block and t > 1 preserves weights in the point-weighted design. The u.i.s. of such a point-weighted design is shown to be a block design if and only if every point is assigned the same weight. A necessary and sufficient condition is obtained for the assignment of weights in any point-weighted design to be essentially uniquely determined by the u.i.s. Chapter 4 considers t-{v, k, Aj W) point-weighted designs in which all of the points apart from a 'special' point have the same weight. It is shown that when v > k the weight of the special point is an integer multiple of the weight assigned to all the other points. A class of these point-weighted designs is demonstrated to be equivalent to a class of group-divisible designs with specific parameters. The final chapter uses the procedure of point-complementing incidence structures to construct point-weighted designs. Trivial point-weighted designs are defined and a necessary and sufficient condition for the existence of a member of a certain class of these is obtained. A correspondence between this class of point-weighted designs and certain trivial block designs is given using point-complementing.

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